Here's something most business owners don't realise until it's too late: the ATO will not remind you your BAS is due. There's no email, no text, no letter in the mail. The due date passes, the penalty clock starts, and you find out when the assessment arrives.
This article lays out every BAS due date for 2025–26 so you can put them in your calendar now — before one of them catches you out.
The quarterly BAS schedule for 2025–26
Most businesses lodge quarterly. Here are the four due dates for this financial year:
| Quarter | Period | Due date (self-lodger) |
|---|---|---|
| Q1 | 1 July – 30 September 2025 | 28 October 2025 |
| Q2 | 1 October – 31 December 2025 | 28 February 2026 |
| Q3 | 1 January – 31 March 2026 | 28 April 2026 |
| Q4 | 1 April – 30 June 2026 | 28 July 2026 |
One practical note: if the 28th falls on a weekend or public holiday, the due date rolls to the next business day. Check your state's public holiday calendar against these dates, particularly for Q3 — April has several.
Monthly PAYG IAS: a separate obligation
If you withhold PAYG from your employees' wages, you may also have a monthly Instalment Activity Statement (IAS) obligation. For most businesses, the IAS is due by the 21st of the following month.
This runs separately to your quarterly BAS. Missing an IAS while staying on top of your BAS is a surprisingly common oversight — particularly for businesses that manage their own payroll manually.
"The ATO issues over $500 million in late lodgement penalties each year in Australia. Most of them are avoidable."
What happens when you miss a due date
Two things happen immediately when you miss a BAS due date. First, the General Interest Charge (GIC) starts accruing on any tax owing. It compounds daily. Second, if you haven't lodged, the ATO can issue a Failure to Lodge (FTL) penalty.
The FTL penalty works like this:
- 1 penalty unit ($330) for every 28 days the lodgement is overdue
- Capped at 5 penalty units — a maximum of $1,650
- Small businesses get a one-unit threshold before the penalty kicks in, but that's only 28 days' grace
These aren't punishing numbers — but they add up. A BAS that's four months overdue can carry $990 in FTL penalties before you've even looked at the GIC on what you owe.
Already behind? Read this first.
Voluntary disclosure before the ATO contacts you typically results in full or partial remission of penalties. Don't wait for them to chase you — contact a registered BAS agent first. We handle the disclosure and the catch-up together.
The deferral advantage of using a registered BAS agent
This is the part most business owners haven't heard. Registered BAS agents — agents registered with the Tax Practitioners Board — can access the TPB lodgement program. This gives clients extended due dates that self-lodgers simply don't have access to.
In practice, that usually means one to two extra months on each quarterly lodgement. For a business going through a difficult quarter — a major reconciliation backlog, a staff change, a messy bank feed — that extra time is genuinely useful. It's not a loophole. It's a legitimate part of how the ATO's lodgement system works.
The extended dates aren't published publicly and aren't available to businesses lodging directly through myGov or the ATO business portal. They're only available through an agent.
Don't try to catch up on your own
If you've missed a lodgement — one quarter or several — don't try to reconstruct and submit everything yourself without advice. The ATO responds far better to proactive contact through a registered agent than to late lodgements arriving without explanation.
We've helped Melbourne and Geelong businesses clean up multi-year backlogs. The outcome is almost always better when you come forward before they come to you. It starts with a phone call.
Antoinette is a Registered BAS Agent — #26211942 — and has been handling BAS lodgements since ALC was founded in 2012. If your BAS situation is more complicated than the calendar above, a free 15-minute call is the right first step.
